a blog by Oliver Peters

Grading through digital bipacks

When you hear someone use the term bipack, you think they are making the word up or just BS’ing you. In fact, bipack refers to an old technique used to create in-camera film effects. Film timers also used the technique to create certain color effects. In modern times, we are really referring to ways that involve blending or superimposing images and this has a direct relationship on tricks you can use in color correction.

The concept of blending two images with different values is a lot like working with layers and blend modes in Photoshop. Some color correction applications, like SpeedGrade, also use a Photoshop-style system of layers. You aren’t limited to color correction applications, though, because these exact same tricks can be used in any NLE. For example, editors have frequently built a look referred to as “instant sex”, which is a technique for adding highlight glows by compositing copies of the same clip on two video layers. The process is easiest with NLEs and compositors like Motion or After Effects that offer composite modes. I find Apple Final Cut Pro X to be a good NLE for these tricks, because the interface design makes it easy to blend and adjust two stacked clips.

I’ll cover several quick examples of how you might use this technique. (Click any of these images for an expanded view.) For clips, I’ve grabbed shots from Afterglow, a short film photographed by John Brawley to promote the release of the Blackmagic Cinema Camera. The source clips are QuickTime ProRes files was a BMD Film (flat, log) gamma profile. To these I’ve added a Pomfort LUT filter normally used for ARRI Alexa Log-C. This corrects the clips back to their intended REC 709 appearance and becomes my starting point.

To stack clips in FCP X, simply edit the clip to the primary storyline and the option-drag it up to duplicate a version as an in-sync, connected clip. Since composite modes often create illegal video levels, I place an adjustment layer clip (a modified Motion title) on top, with a broadcast safe filter added to it.

In this first example, the bottom clip is changed to black-and-white by reducing the saturation in the FCP X color board. The top clip’s composite mode is set to Soft Light. Grading for the right tonal qualities becomes a dance between the settings on the two layers and the opacity value of the top clip’s compositing mode.

If I add a Gaussian blur to the lower clip, change the compositing mode of the top clip to Overlay and tweak the color board settings of the two clips, the look changes from harsh to glamour.

In this billiards shot I’m using the Soft Light mode again, but this time I have tinted the lower clip to a slight teal cast. The top clip is a vibrant orange, but the combination of the two ends up with the more normal-looking and popular orange-and-teal grade.

In this balcony shot I’m using the Overlay mode and have added a slight directional blur to the top layer. The bottom layer is desaturated with a slight tint while the top layer is more vibrant. Combined they have a high-contrast, bleached look.

In this final example, I’ve reversed some items. The top layer is set to the Multiply mode at 80% opacity and I’ve made it black-and-white. The color correction is again a matter of compensating between the two layers to get the right feel.

When I add a Gaussian blur to the top clip the look changes from harsh to a nice, diffused appearance.